1. Field of the Invention
The present invention relates generally to an apparatus and method for a Multicast and Broadcast Service (MBS) in a Broadband Wireless Access (BWA) system, and in particular, to an apparatus and method for simultaneously providing an MBS service and a unicast service in a BWA system.
2. Description of the Related Art
As generally known in the art, communication systems have been primarily developed for voice communication services, but they are also evolving to provide data services and various multimedia services. However, conventional communication systems, which are mainly directed to providing voice communication services, have a narrow data transmission bandwidth and require a high subscription fee. For these reasons, they cannot satisfy diversified user demands. Furthermore, in line with rapid development in the communication industry and ever-increasing demands on Internet services, it is important to provide communication systems capable of providing Internet services efficiently. As a result of these trends, BWA systems having a bandwidth large enough to both satisfy the increasing user demands and provide efficient Internet services have been proposed.
In addition to providing voice communication services, BWA systems aim at supporting a variety of low-speed as well as high-speed data services and multimedia application services (e.g., high-quality moving pictures) in combination. Based on wireless media using a broadband of 2 GHz, 5 GHz, 26 GHz, or 60 GHz, BWA systems are able to access the Public Switched Telephone Network (PSTN), the Public Switched Data Network (PSDN), the Internet, the International Mobile Telecommunications-2000 (IMT-2000) network, and the Asynchronous Transfer Mode (ATM) network in a mobile or stationary environment. In other words, BWA systems can support a channel transmission rate of at least 2 Mbps. BWA systems may be classified into broadband wireless local loops, broadband mobile access networks, and high-speed wireless Local Area Networks (LANs) according to the terminal's mobility (stationary or mobile), communication environment (indoor or outdoor), and channel transmission rate.
Examples of principal services of the BWA systems are Internet services, Voice over IP (VoIP) services, and non-real-time streaming services. Recently, a Multicast and Broadcast Service (MBS) has emerged as a new real-time broadcast service. The MBS service can provide two-way data communication while supporting mobility unlike a Digital Multimedia Broadcasting (DMB) service where only one-way communication is provided.
The MBS can provide video broadcast services, such as news, dramas and sports game, and data services such as radio music broadcast and real-time traffic information. Compared to the conventional unicast service, the MBS service has the following characteristics.
(1) Formality: The unicast service generates connections and transmits/receives traffic according to the request/need of the users, whereas the MBS service always transmits traffic for a predetermined time (e.g., from 6 a.m. to 10 p.m.) regardless of reception by the users.
(2) Transmission rate: The MBS traffic is used mainly for multimedia services, and has a fixed transmission rate, packet size, and inter-packet interval.
(3) Resource allocation: The MBS traffic is serviced for a predetermined broadcast time using pre-allocated resources. That is, dedicated resources are reserved for MBS service during a predetermined broadcast time, which reduces resources for the unicast service.
As described above, because the MBS service causes a change in the available resources for the unicast service, a Quality of Service (QoS) framework must consider the following things due to the MBS service.
(1) Before the start of the broadcast: If the unicast service occupies all available resources, MBS resources must be provided before the start of the broadcast for a smooth broadcast service.
(2) During the broadcast: Resources for the unicast service are reduced during the MBS service.
(3) After the end of the broadcast: Resources allocated for the MBS service must be released.
If the MBS resources fail to be provided before the start of the broadcast, the quality of the broadcast service may be degraded and low-priority unicast service may be disconnected. Also, resources are wasted if the MBS resources are not released after the end of the broadcast.